It's one of these (in the 'army green' - which is more of a grey/green colour):
https://www.amazon.co.uk/SUVOM-Vint...vas+backpack&qid=1558969970&s=gateway&sr=8-60
Being waxed canvas it holds its shape very well.
I'd say it's about 25L.
What I liked about it were the external pouches (one on each side plus one on the front) plus it has an internal sleeve plus a couple of smaller internal pockets.
The downside were the buckles.
Well, not the buckles per se. As supplied the buckles are functioning buckles but they actually have magnets on the back, which is how you open it.
I didn't like that. So I took the magnets off. I then fixed the dead end of the straps to the bag. I could have stitched it but what I did was make, effectively, some large staples out of some brass. They then went through the leather 'dead end' (don't know if that's the right word) and through the pack and were folded over inside.
I can show you some pictures if that doesn't make sense. It really was very simple. And it means the buckles now function as buckles.
It's a great bag, I love it. I've had canvas packs in the past but whilst I love the look of them, in practice, they are just shapeless sacks of ****.
But this particular pack, being waxed, is quite rigid and holds its shape and the external and internal pockets allow some modularity rather than everything just rolling around inside.
I've had it about a year now and it's still all in one piece and showing no sign of wear and tear.